Effect of R21D10 on Fg binding to fixed platelets. (A) Washed platelets were treated with phosphate-buffered saline, EDTA, or 1 μM eptifibatide for 30 minutes at room temperature. The platelets were then incubated with R21D10 (40 μg/mL) or 7E3 (10 μg/mL) for 15 minutes, fixed with 1% paraformaldehyde for 40 minutes, and incubated with 5 mM glycine for 5 minutes at room temperature. The platelets were washed 3 times with HEPES-buffered modified Tyrode's solution (HBMT) and resuspended. Alexa Fluor 488 Fg (200 μg/mL) was added to the platelets for 30 minutes at room temperature and Fg binding was detected by flow cytometry. (B) Washed platelets were treated, fixed, and washed, as in panel A. After resuspension in HBMT, the platelets were incubated with either R21D10 or 7E3 for 15 minutes, and Alexa Fluor 488–labeled Fg binding was detected as in panel A. (C) Statistical analysis of 4 experiments conducted using blood obtained from 4 donors. ∗∗P < .01; ∗∗∗∗P < .0001.